It is given that, l+3m+5n=0 l=−(3m+5n) …… (I) Thus, 5(−3m−5n)m−2mn+6(−3m−5n)n=0 −15m2−25mn−2mn−18mn−30n2=0 15m2+45mn+30n2=0 m2+3mn+2n2=0 Solve further, (m+n)(m+2n)=0 m=−n,−2n When m=−n, then l=−2n. Thus, the DR 'S are 2,-1,1 . When m=−2n, then l=n . Thus, the DR'S are 1,1,-2 . Now,